The invention disclosed relates to the testing of formations in oil wells, and is most advantageous in conducting tests in offshore oil wells where it is desirable to conduct a well testing program with a minimum of tool string manipulation, and preferably with the blowout preventers closed during a major portion of the program.
It is known in the art that sampler valves and tester valves for testing the productivity of oil wells may be operated by applying pressure increases to the fluid in the annulus of the well. For instance, U.S. Pat. No. 3,664,415 to Wray et al. discloses a sampler valve which is operated by applying annulus pressure increases against a piston in opposition to a predetermined charge of inert gas. When the annulus pressure overcomes the gas pressure, the piston moves to open a sampler valve thereby allowing formation fluid to flow into a sample chamber contained within the tool, and into the testing string facilitating production measurements and testing.
U.S. Pat. No. 3,858,649 to Holden et al. also discloses a sampler apparatus which is opened and closed by applying pressure changes to the fluid in the well annulus. A gas pressure supplementing means is included in the aforementioned Holden patent to avoid the necessity of determining the proper gas operating pressure at the testing depth and to allow the use of lower inert gas pressure at the surface. U.S. Pat. No. 3,856,085 to Holden et al. provides a full opening testing apparatus containing a pressurized inert gas whose pressure is supplemented as the apparatus is lowered into the well, and which is operable by increasing and decreasing the pressure of the fluid in the well annulus.
The apparatus of the above mentioned patents all require compressed inert gas as a spring medium and therefore require special equipment and training for the transportation and storage of said compressed gas.
Weight operated tester valves which open after a desired delay are known in the art. One such device is disclosed in U.S. Pat. No. 3,814,182 to Giroux. However, this device used alone requires that the test string be manipulated up and down in order to operate the valve mechanism. It is desirable in conducting a test, for safety reasons, to maintain the blowout preventers closed to the maximum extent possible. This cannot be done if the test string must be manipulated to operate the valve.
Slip joints to allow movement in the test string are known, but have heretofore been used to minimize the transmission of wave action to the packer and valving mechanisms. One such slip joint is disclosed in U.S. Pat. No. 3,354,950 to Hyde. However, these slip joints have not been used to allow motion in the test string after the blowout preventer is closed in order to facilitate the operation of a weight and pressure responsive valve mechanism which lifts the lower portion of the test string in response to pressure increases in the well annulus. In addition, the slip joint disclosed in the Hyde patent mentioned above tends to affect the apparent weight acting on the weight and pressure responsive valve responsive to the initial fluid in the test string and the fluid pressure in the well annulus. Thus, if the initial fluid is displaced by lower density formation fluid, or when the fluid pressure in the well annulus is changed, the apparent weight acting on said weight and pressure operated valve may be changed sufficiently that the weight and pressure operated valve may not operate correctly as desired.
The present invention comprises a weight and pressure responsive valve controlling fluid communication in an oil well including a housing having an internal sealed chamber and an operating mandrel movable in one direction responsive to weight, and movable in a second opposite direction responsive to pressure in said sealed chamber and to the pressure of the fluid in the annulus of the well, wherein movement of the mandrel in the first direction expands the sealed chamber reducing the pressure therein. Said valve is closed when sufficient weight acts upon the valve to move the operating mandrel in the first direction, and to expand the sealed chamber. When sufficient pressure is added to the annulus of the well, the mandrel moves in said second direction responsive to the pressure in the annulus and the reduced pressure in the sealed chamber to overcome said weight, thereby closing said valve. Thus a valve results which is operable by setting a predetermined amount of weight on a packer isolating a formation to be tested, and by increasing and decreasing the pressure of the fluid in the well annulus.
The weight and pressure responsive valve additionally is a full opening device and is separable into an operating unit and a valving unit. These units are joined by a connecting joint which assures proper alignment between the units.
The operating mandrel is further designed to deform a sufficient amount to allow for design tolerances, thus protecting the valve operating mechanism from excess stresses. Further, the operating mandrel and the housing of the apparatus provides for the transmission of torque, thus allowing the use of packers operable by rotation.
The test string of the invention includes a normally closed, weight operated valve which opens responsive to suficient weight acting upon the valve after a preset delay. The weight operated valve is also a full opening valve, thus giving a testing string which has an unobstructed, fully open interior bore when both the weight and pressure responsive valve, and the weight operated valve are open. The delayed opening feature allows sufficient time for the weight and pressure operated valve to close initially before the weight operated valve opens, thus insuring that the interior bore will not open prematurely.
The slip joint provided in the testing string allows movement in the test string after the blowout preventer is closed, thus allowing the weight and pressure responsive valve to be operated by applications of pressure to the annulus with the blowout preventers closed. The slip joint determines by its position the weight supported by the packer, thus providing for changing the weight acting on said weight and pressure responsive valve and said weight operated valve, thereby providing a testing string which may be used at various depths and with various densities of fluids in the well. The slip joint is additionally compatible with the weight and pressure responsive valve to nullify the effects of fluid pressure in the interior bore of the testing string, and pressure changes in the well annulus, in order that the apparent weight acting on weight and pressure responsive valve will not change when formation fluid displaces the original fluid in the string or when the fluid pressure in the well annulus is changed. The slip joint also provides for torque transmission.
The testing string incorporating the disclosed invention allows a formation to be tested by lowering a testing string into a fluid filled bore; setting a packer to isolate the formation to be tested; setting a predetermined amount of weight on the packer to close a normally open weight and pressure responsive valve; after a preset delay, opening a normally closed weight operated valve responsive to the added weight; and, opening and closing the weight and pressure responsive valve by increasing and decreasing the pressure of the fluid in the well bore.
The interior bore of the test string may be fully open, thus allowing the passage of well tools through the test string when both valves are open. A slip joint absorbs the motion of the weight and pressure responsive valve during its operation, thus allowing the testing program to be conducted while the blowout preventers are closed.